Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/POCO/Data/ODBC/src/ConnectionHandle.cpp

@@ -0,0 +1,57 @@
+//
+// ConnectionHandle.cpp
+//
+// Library: Data/ODBC
+// Package: ODBC
+// Module:  ConnectionHandle
+//
+// Copyright (c) 2006, Applied Informatics Software Engineering GmbH
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#include "Poco/Data/ODBC/ConnectionHandle.h"
+#include "Poco/Data/ODBC/Utility.h"
+#include "Poco/Data/ODBC/ODBCException.h"
+
+
+namespace Poco {
+namespace Data {
+namespace ODBC {
+
+
+ConnectionHandle::ConnectionHandle(EnvironmentHandle* pEnvironment): 
+	_pEnvironment(pEnvironment ? pEnvironment : new EnvironmentHandle),
+	_hdbc(SQL_NULL_HDBC), 
+	_ownsEnvironment(pEnvironment ? false : true)
+{
+	if (Utility::isError(SQLAllocHandle(SQL_HANDLE_DBC, 
+		_pEnvironment->handle(), 
+		&_hdbc))) 
+	{
+		throw ODBCException("Could not allocate connection handle.");
+	}
+}
+
+
+ConnectionHandle::~ConnectionHandle()
+{
+	try
+	{
+		SQLDisconnect(_hdbc);
+		SQLRETURN rc = SQLFreeHandle(SQL_HANDLE_DBC, _hdbc);
+
+		if (_ownsEnvironment) delete _pEnvironment;
+
+		poco_assert (!Utility::isError(rc));
+	}
+	catch (...)
+	{
+		poco_unexpected();
+	}
+}
+
+
+} } } // namespace Poco::Data::ODBC